<html>
 <head> 
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
  <style type="text/css">
    body{
      margin:0px auto;
    }
    #content {
      position: absolute;
      left: 50%;
      top: 35%;
      transform: translate(-50%, -50%);
    }
  </style> 
  <title></title> 
 </head> 
 <body> 
  <div id="content">
    这是一个html页面
  </div>  
 </body>
</html>